Organocatalytic, Asymmetric [2+2+2] Annulation to Construct Six-Membered Spirocyclic Oxindoles with Six Continuous Stereogenic Centers

Abstract

Lactols and cyclic hemiaminals were directly used in a one-pot organo/organo dual catalytic system induced [2+2+2] tandem reaction for the asymmetric construction of six-membered carbocycles. The enamine-based stereoselective Michael addition of lactols or cyclic hemiaminals to electron-deficient olefinic oxindole motifs provided chiral C4 components, which were further combined with triethylamine catalyzed Michael/Henry sequential reactions affording spirocyclic oxindole derivatives containing six continuous stereogenic centers with excellent enantioselectivities as a single diastereoisomer. All these desired products have versatile molecular complexity, which might have potential applications in synthetic organic chemistry and the pharmaceutical industry.

Keywords

• asymmetric organocatalysis
• tandem reaction
• lactol
• cyclic hemiaminal
• [2+2+2] annulation
• spirocyclic oxindole